Related Field
The present invention relates to a method for additive manufacturing of a three dimensional article by successively fusing individual layers of powder material.
Description of Related Art
Freeform fabrication or additive manufacturing is a method for forming three-dimensional articles through successive fusion of chosen parts of powder layers applied to a worktable.
An additive manufacturing apparatus may comprise a work table on which the three-dimensional article is to be formed, a powder dispenser or powder distributor, arranged to lay down a thin layer of powder on the work table for the formation of a powder bed, a high energy beam for delivering energy to the powder whereby fusion of the powder takes place, elements for control of the energy given off by the energy beam over the powder bed for the formation of a cross section of the three-dimensional article through fusion of parts of the powder bed, and a controlling computer, in which information is stored concerning consecutive cross sections of the three-dimensional article. A three-dimensional article is formed through consecutive fusions of consecutively formed cross sections of powder layers, successively laid down by the powder dispenser.
In additive manufacturing a short manufacturing time and high quality of the finalized product is of outmost importance. Desired material properties of the final product may depend on the ability to control the fusion process. One important parameter is the ability to fast and accurately control the actual beam output during the fusion process. In most electron beam sources the output current from the source may vary over time. If not having a full control of this variation in the beam current over time, there is a great risk that the actual material properties of the final product will deviate from the desired material properties.